The present invention relates to a novel heat shrinkable container especially useful for food stuffs and the process for manufacturing the same.
Barrier laminates have been used in the past to protect food stuffs from spoilage. In this regard, reference is made to U.S. Pat. No. 3,741,253 which describes a laminate using Saran as a sealing middle layer between an inner layer of irradiated ethylene vinyl acetate polymer and an outer layer of ethylene/ vinyl acetate polymer which is not cross linked by irradiation. Although this laminate solves several of the problems of permeability of oxygen and water, it should be noted that the packaging film described in this patent does not possess a shipping abuse resistant outer layer which renders the film susceptible to loss of integrity through abrasion. In addition, the cross linked inner layer is hard to self weld to prevent breakage by puncturing in the process of packaging. The process of manufacturing the film of the prior art, heretofore identified, is a coating process which is more expensive and energy consuming than a coextrusion process in that more dies are required and a large amount of plasticizer is necessary in its production. The latter step reduces the oxygen and water barriers of the inner Saran layer. Also, it should be noted that a coating process, despite the most careful manufacturing technique, traps air between the layers which causes a bad appearance and causes weakening through separation and delamination of the same. Also, sealing the laminate of the prior art presents a problem in that the soft outer layer tends to stick to the jaws of the sealing devices which necessitates the employment of mechanical crimping, a slower and more expensive method of manufacture. Moreover, crystallization can occur in the Saran layer if excess heat or plasticization reaches the same. This occurrence will result in decrease in elongation of the film during the biaxially orientation process and clip fracturing during packaging.
A heat shrinkable container which solves the problems of the prior art hereinabove described would be a great advance in the food packaging industry.